A fluid-applying device for applying a fluid to a teat of a dairy animal. The fluid-applying device comprises a fluid detector for determining a fluid application pattern of the fluid on the teat of the dairy animal. The fluid detector comprises a computer loaded with comparing software for comparing the determined fluid application pattern with a previously stored reference criterion, for emitting a comparison signal which is indicative of the comparison result, and for determining the teat length, the tip of the teat, and the fluid application distance, measured from the tip of the teat, over which the fluid has been applied to the teat, and for emitting a fluid signal comprising data in relation to the determined fluid application distance. The reference criterion may be a threshold distance with which the determined fluid application distance is compared.